Campbell-scientific CS547 Conductivity and Temperature Probe and A547 Manual do Utilizador descarregar pdf (Página 18)

CS547 Conductivity and Temperature Probe and A547 Interface

8.2 Temperature Measurement Error

The overall probe accuracy is a combination of the thermistor's interchangeability

specification, the precision of the bridge resistors, and the polynomial error. In a

"worst case" all errors add to an accuracy of ±0.4°C over the range of -24° to 48°C

and ±0.9°C over the range of -38°C to 53°C. The major error component is the

interchangeability specification of the thermistor, tabulated in Table 8.2-1. For the

range of 0° to 50°C the interchangeability error is predominantly offset and can be

determined with a single point calibration. Compensation can then be done with an

offset entered in the measurement instruction. The bridge resistors are 0.1%

tolerance with a 10 ppm temperature coefficient. Polynomial errors are tabulated in

Table 8.2-2 and plotted in Figure 8.2-1.

TABLE 8.2-1. Thermistor

Interchangeability Specification

Temperature

Temperature (°C) Tolerance (±°C)

−40

0.40

−30

0.40

−20

0.32

−10

0.25

0 to +50 0.20

TABLE 8.2-2. Polynomial Error

-40 to +56

<±1.0°C

-38 to +53

<±0.5°C

-24 to +48

<±0.1°C

FIGURE 8.2-1. Error Produced by Polynomial Fit to Published Values

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 24 25 26

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